1. Field of the Invention
The present invention relates generally to mobile communication systems, and in particular, to a device and method for a mobile station for receiving signals transmitted from a base station having a transmission diversity function.
2. Description of the Related Art
In a typical mobile communication system, a base station and a mobile station each have one antenna to exchange data with each other. In such a design configuration, when a transmission channel fades, as when an obstacle, such as a building, is between the mobile station and the base station, the communication quality deteriorates. To counteract this from occurring, a diversity technique is generally used. The diversity technique improves the performance of the mobile communication system.
To transmit signals from a mobile station to a base station via a reverse link, a receiver diversity technique can be used in which multiple receiving antennas are installed at the base station. In addition, for transmitting signals from the base station to the mobile station via a forward link, it is possible to use a transmission diversity technique for transmitting the signals via multiple transmission antennas installed at the base station. Where the base station has a transmission diversity function, the mobile station can use only one antenna for diversity effect.
In practice, however, it is difficult to install multiple receiving antennas in the small mobile station to configure the mobile station to optimally perform using the receiver diversity technique during forward link communications. Even though receiving antennas can be installed in the mobile station, the small size of the mobile station limits the distance between the receiving antennas, and thereby, reducing a diversity gain. In addition, when multiple antennas are installed in the mobile station, it is necessary to provide separate schemes for receiving forward link signals and transmitting reverse link signals via the corresponding antennas, causing an increase in size and cost of the mobile station. For these reasons, the mobile communication system generally uses transmission diversity techniques rather than the receiver diversity techniques.
It is, therefore, an object of the present invention to provide a receiving device and method for a mobile station for receiving signals transmitted from a base station having a time-switched transmission diversity (TSTD) function.
It is another object of the present invention to provide a receiving device and method for a mobile station for receiving signals transmitted from a base station via multiple transmission antennas by using a single receiving antenna.
It is further another object of the present invention to provide a device and method for a mobile station for receiving a TSTD signal and a non-TSTD signal transmitted from a base station and estimating channel conditions for the respective paths according to operation modes.
It is still another object of the present invention to provide a device and method for a mobile station for estimating a receiving power of signals transmitted from a base station having a TSTD function.
It is still further another object of the present invention to provide a device and method for a mobile station for estimating a receiving power of a TSTD signal and a non-TSTD signal transmitted from a base station having a TSTD function.
These and other objects are realized by the present invention where a device and methods are provided for a mobile station for receiving and processing data transmitted in a time-switched transmission diversity (TSTD) function from a base station.
In accordance with one aspect of the present invention, a receiving device for a mobile communication system includes a despreader for despreading channel signals which have been transmitted in a time-switched transmission diversity (TSTD) mode of operation; a pilot separator for separating a pilot signal from the despread channel signals; a channel estimator for generating a channel estimation signal by selecting pilot signals transmitted from a same antenna of a transmitter according to a TSTD pattern of the transmitter; and a compensator for compensating the channel signals with the channel estimation signal.
In accordance with another aspect of the present invention, a receiving device for a mobile communication system includes a despreader for despreading channel signals which have been transmitted in a TSTD mode of operation; a pilot separator for separation a pilot signal from the despread channel signals; a signal power estimator for generating a signal power estimation signal by selecting pilot signals transmitted from a same antenna of a transmitter according to a TSTD pattern of the transmitter; an interference power estimator for generating an interference power estimation signal from the channel signals transmitted in the TSTD mode of operation; and a decider for deciding power of a received signal by operating the signal power estimation signal and the interference power estimation signal.